Left ventricular hypertrophy (LVH), such as occurs in hypertension, carries an increased risk for cardiovascular events. Clinical evidence indicates that inhibition and regression of LVH is associated with improved cardiac function and a reduced risk of cardiovascular complications. MicroRNAs (miRNAs) are short endogenous RNAs that can regulate multiple genes. miRNA levels have been shown to significantly change in diseased human hearts. Modulation of miRNAs to treat cardiovascular disease is seen as a potentially powerful clinical tool; e.g. knockdown of miR-23a, which promotes hypertrophy, was shown to blunt cardiac hypertrophy in a hypertensive murine model. However, the lack of effective, safe, non-immunogenic methods for delivery of miRNA mimics or inhibitors limits clinical translation. Ultrasound targeted microbubble destruction (UTMD) represents an attractive non-immunogenic, theranostic delivery strategy to locally modulate miRNA levels in the heart. UTMD has been shown to enhance endocytosis and can also induce transient pores to form in cell membranes as a result of microbubble oscillation and collapse, potentially allowing nucleotides to enter the cytoplasm directly. The objective of this proposal is to develop a platform utilizing ultrasound and microbubbles to regulate miRNA levels in the heart. This platform can potentially be used to deliver any miRNA mimic or inhibitor of interest. Accordingly, we hypothesize that UTMD-mediated delivery of an antagomir directed against pro-hypertrophic miR-23a will attenuate phenylephrine-induced cardiac hypertrophy. Our 3 Specific Aims are to determine: (1) if UTMD can deliver an antagomir against a prohypertrophic miRNA to cardiomyocytes in vitro; (2) if UTMD can deliver an antagomir against a pro-hypertrophic miRNA to a beating, hypertensive heart; and (3) the mechanism of action involved in UTMD-mediated antagomir release from microbubbles. The efficacy of UTMD under varying acoustic conditions will be evaluated with respect to expression levels of miR-23a and its downstream targets, cardiomyocyte and ventricular hypertrophy, and overall cardiac function. Novel ultra high speed imaging of antagomir release by microbubbles under the influence of ultrasound will provide insights into mechanisms underlying effective UTMD regimes. Ultimately, this research program will provide a foundation for a clinically translatable targeted delivery platform to therapeuticaly regulate miRNA levels in the heart.